Expression of visfatin in gingival crevicular fluid and gingival tissues in different periodontal conditions: a cross-sectional study.

BACKGROUND: Studies have shown that visfatin is an inflammatory factor closely related to periodontitis. We examined the levels of visfatin in gingival crevicular fluid (GCF) and gingival tissues under different periodontal conditions, in order to provide more theoretical basis for exploring the role of visfatin in the pathogenesis of periodontitis. METHODS: We enrolled 87 subjects, with 43 in the chronic periodontitis (CP) group, 21 in the chronic gingivitis (CG) group, and 23 in the periodontal health (PH) group. Periodontal indexes (PD, AL, PLI, and BI) were recorded. GCF samples were collected for visfatin quantification, and gingival tissues were assessed via immunohistochemical staining. RESULTS: Visfatin levels in GCF decreased sequentially from CP to CG and PH groups, with statistically significant differences (P < 0.05). The CP group exhibited the highest visfatin levels, while the PH group had the lowest. Gingival tissues showed a similar trend, with significant differences between groups (P < 0.001). Periodontal indexes were positively correlated with visfatin levels in both GCF and gingival tissues (P < 0.001). A strong positive correlation was observed between visfatin levels in GCF and gingival tissues (rs = 0.772, P < 0.001). CONCLUSION: Greater periodontal destruction corresponded to higher visfatin levels in GCF and gingival tissues, indicating their potential collaboration in damaging periodontal tissues. Visfatin emerges as a promising biomarker for periodontitis and may play a role in its pathogenesis.

Enzymatic Cleaning Mitigates Polysaccharide-Induced Refouling of RO Membrane: Evidence from Foulant Layer Structure and Microbial Dynamics.

Traditional harsh chemical cleaning-in-place (CIP) is corrosive to membranes but has limited inhibition on refouling, a tough problem for long-term operation of reverse osmosis (RO). Mild enzymatic cleaning (at pH 9) is a promising alternative but lacks long-term verification and insightful elucidation. In this study, we investigated the instantaneous efficiency, postcleaning refouling, and biological effect of enzymatic CIP (compounded with lipase, protease, and sodium dodecyl sulfate) on practical RO membranes during a 500 h multicycle operation. The enzymatic CIP had an average cleaning efficiency of 77%, which is comparable to a commercial harsh CIP benchmark (pH > 12). It mitigated refouling by shaping the biofilm into a loose and porous architecture where newly arrived organics conformed standard blocking, whereas harsh chemicals rendered a smooth and dense gel layer with quick refouling in intermediate blocking or cake filtration mode. Such structural disparities were dominated by polysaccharides according to quantitative chemical analyses. Gene sequencing and ecological network analysis further proved that the behavior of polysaccharide-related keystone species (such as Sphingomonas and Xanthomonas) significantly changed after long-term enzymatic treatment. In this regard, the mild selective pressure of enzymatic reagents can directionally regulate microbial dynamics, alter foulant layer structure via bio-organic synchronicity, mitigate refouling, and eventually improve the sustainability of RO operation.

A Y(III)-based Metal-Organic Framework as a Carrier in Chemodynamic Therapy.

A biocompatible Y(III)-based metal-organic framework [Y4(TATB)2]·(DMF)3.5·(H2O) (ZJU-16, H3TATB= 4,4',4''-(1,3,5-triazine-2,4,6-triyl) tribenzoic acid) was synthesized, and it was adopted to load Mn2+ for chemodynamic therapy. Meanwhile, ibuprofen sodium (IBUNa), an anti-inflammatory drug, was introduced to increase the amount of Mn2+ (about 5.66 wt %) due to the low loading capacity of Mn2+. Mn&IBUNa@ZJU-16 which was loaded by Mn2+ and IBUNa exhibited significant effects of chemodynamic therapy and excellent inhibition of the 4T1 tumor cell growth, implying its long-term prospects in chemodynamic therapy and its possibility in bimodal cancer therapy.

Electrically Tuning Ultrafiltration Behavior for Efficient Water Purification.

Conventional ultrafiltration (UF) technology suffers from membrane fouling and limited separation performance. This work demonstrates a novel electrical tuning strategy to improve the separation efficiency of the UF process. An electrically enhanced UF (EUF) system with two sets of oppositely placed membrane-electrode modules was set up. A series of multicycle treatment experiments were conducted to reveal the performance and tuning mechanism of the EUF system. The applied electrical tuning operation brought about an up to 68% reduction of average transmembrane pressure increasing rate (Rp), indicating a strong capability in inhibiting membrane fouling. This fouling reduction can be mainly ascribed to the applied electrophoretic force, changes in solution chemistry, and generation of peroxide, which repulses foulants away from the membrane, hampers foulant adsorption owing to enhanced electrostatic repulsion, and degrades foulants, respectively. The 1.2 V voltage was identified as an effective voltage for stably inhibiting membrane fouling. Besides, the electrical tuning operation led to an up to ∼32% increase in foulant retention rate (φ) owing to both non-Faradaic effects (including electrosorption and electrophoretic repulsion) and Faradaic oxidative degradation. Moreover, the electrical tuning operation allowed a remarkable desalination capability with a significantly higher desalination rate and an up to ∼43% greater salt adsorption capacity as compared with a conventional capacitive deionization process. Additionally, the EUF system achieved a good performance in removing heavy metals (Ag, Cu, Pb, Se, and Sb). The overall enhanced EUF performance suggests promising prospects for practical applications.

Roles of membrane and organic fouling layers on the removal of endocrine disrupting chemicals in microfiltration.

To understand the adsorption behavior of endocrine disrupting chemicals (EDCs) is important for enhancing the treatment performance and preventing potential secondary pollution caused by EDCs desorption in a microfiltration system. The dynamic adsorption of four representative EDCs, namely estriol (E3), 17ß-estradiol (E2), 17α-ethynylestradiol (EE2), and 4-nonylphenol (4-NP) in a microfiltration system was investigated using the Thomas' model. The product of the equilibrium constant and the total adsorption capacity of the membrane, Ka, for E3, E2, EE2, and 4-NP were 4.91, 9.78, 15.6, and 826, respectively, strongly correlating with the compound octanol-water partition coefficient (KOW). Adsorption appeared to be enhanced when organic fouling formed on the surface of membrane, indicating the role of an additional adsorption column for EDCs acted by a fouling layer in microfiltration. Results of a comparison between the Ka values for clean membrane and fouled membrane illustrated that the significant contribution made by fouling layers may be attributed to the foulant layer's hydrophobicity (in the case of calcium humate layer) and thickness (in the case of calcium alginate layer). This study provided a novel perspective to quantitatively analyze the dynamic adsorption behavior of trace pollutants in membrane process.

Enhanced anaerobic digestion performance and sludge filterability by membrane microaeration for anaerobic membrane bioreactor application.

Slow dissolution/hydrolysis of insoluble/macromolecular organics and poor sludge filterability restrict the application potential of anaerobic membrane bioreactor (AnMBR). Bubble-free membrane microaeration was firstly proposed to overcome these obstacles in this study. The batch anaerobic digestion tests feeding insoluble starch and soluble peptone with and without microaeration showed that microaeration led to a 65.7-144.8% increase in methane production and increased critical flux of microfiltration membrane via driving the formation of large sludge flocs and the resultant improvement of sludge settleability. The metagenomic and bioinformatic analyses showed that microaeration significantly enriched the functional genes and bacteria for polysaccharide and protein hydrolysis, microaeration showed little negative effects on the functional genes involved in anaerobic metabolisms, and substrate transfer from starch to peptone significantly affected the functional genes and microbial community. This study demonstrates the dual synergism of microaeration to enhance the dissolution/hydrolysis/acidification of insoluble/macromolecular organics and sludge filterability for AnMBR application.

Triple Sensing Modes for Triggered ß-Galactosidase Activity Assays Based on Kaempferol-Deduced Silicon Nanoparticles and Biological Imaging of MCF-7 Breast Cancer Cells.

ß-Galactosidase (ß-Gala) is an essential biomarker enzyme for early detection of breast tumors and cellular senescence. Creating an accurate way to monitor ß-Gala activity is critical for biological research and early cancer detection. This work used fluorometric, colorimetric, and paper-based color sensing approaches to determine ß-Gala activity effectively. Via the sensing performance, the catalytic activity of ß-Gala resulted in silicon nanoparticles (SiNPs), fluorescent indicators obtained via a one-pot hydrothermal process. As a standard enzymatic hydrolysis product of the substrate, kaempferol 3-O-ß-d-galactopyranoside (KOßDG) caused the fluorometric signal to be attenuated on kaempferol-silicon nanoparticles (K-SiNPs). The sensing methods demonstrated a satisfactory linear response in sensing ß-Gala and a low detection limit. The findings showed the low limit of detection (LOD) as 0.00057 and 0.098 U/mL for fluorometric and colorimetric, respectively. The designed probe was then used to evaluate the catalytic activity of ß-Gala in yogurt and human serum, with recoveries ranging from 98.33 to 107.9%. The designed sensing approach was also applied to biological sample analysis. In contrast, breast cancer cells (MCF-7) were used as a model to test the in vitro toxicity and molecular fluorescence imaging potential of K-SiNPs. Hence, our fluorescent K-SiNPs can be used in the clinic to diagnose breast cellular carcinoma, since they can accurately measure the presence of invasive ductal carcinoma in serologic tests.

Porous titanium-6 aluminum-4 vanadium cage has better osseointegration and less micromotion than a poly-ether-ether-ketone cage in sheep vertebral fusion.

Interbody fusion cages made of poly-ether-ether-ketone (PEEK) have been widely used in clinics for spinal disorders treatment; however, they do not integrate well with surrounding bone tissue. Ti-6Al-4V (Ti) has demonstrated greater osteoconductivity than PEEK, but the traditional Ti cage is generally limited by its much greater elastic modulus (110 GPa) than natural bone (0.05-30 GPa). In this study, we developed a porous Ti cage using electron beam melting (EBM) technique to reduce its elastic modulus and compared its spinal fusion efficacy with a PEEK cage in a preclinical sheep anterior cervical fusion model. A porous Ti cage possesses a fully interconnected porous structure (porosity: 68 ± 5.3%; pore size: 710 ± 42 µm) and a similar Young's modulus as natural bone (2.5 ± 0.2 GPa). When implanted in vivo, the porous Ti cage promoted fast bone ingrowth, achieving similar bone volume fraction at 6 months as the PEEK cage without autograft transplantation. Moreover, it promoted better osteointegration with higher degree (2-10x) of bone-material binding, demonstrated by histomorphometrical analysis, and significantly higher mechanical stability (P < 0.01), shown by biomechanical testing. The porous Ti cage fabricated by EBM could achieve fast bone ingrowth. In addition, it had better osseointegration and superior mechanical stability than the conventional PEEK cage, demonstrating great potential for clinical application.

First report on rhinoceros from the late Neogene Qin Basin of Shanxi, China.

Dihoplus is a rhinoceros distributed across East Asia and Europe from the Late Miocene to Pliocene. This study describes a new skull from the Qin Basin in Shanxi Province, China, referred to as Dihoplus ringstroemi, which has long been debated in taxonomic identity. This skull confirms that D. ringstroemi is an independent species and reveals the presence of the upper incisor and variations in the degree of constriction of the two lingual cusps of upper cheek teeth. In addition, the new skull indicates that the Qin Basin has a late Neogene sediment and fauna comparable to that of the Yushe Basin.

Reproduction of a fossil rhinoceros from 18 mya and origin of litter size in perissodactyls.

Reproductive strategy is among the most important characteristics of organism. Here, we report reproductive strategy of singleton pregnancy of a fossil rhinoceros, Plesiaceratherium gracile, from 18 mya of the Shanwang Basin, China. Dental and body development data revealed that after birth, the calf of P. gracile is breastfed for 2-3 years; at approximately 5 years of age, when the M2 tooth is slightly worn, the female has already reached sexual maturity and attained a size close to that of an adult and could give birth to the first calf. Furthermore, given litter size is phylogenetically conservative and closely correlates with body size, we conclude that the litter size of perissodactyls is determined by the singleton pregnancy since the Eocene. By contrast, other reproductive traits are highly variable and have a different pace of evolution, and traits observed in living rhinoceroses have been evolving at least since 18 mya.

Fast detection of genetic information by an optimized PCR in an interchangeable chip.

In this paper, we report the construction of a polymerase chain reaction (PCR) device for fast amplification and detection of DNA. This device consists of an interchangeable PCR chamber, a temperature control component as well as an optical detection system. The DNA amplification happens on an interchangeable chip with the volumes as low as 1.25 µl, while the heating and cooling rate was as fast as 12.7°C/second ensuring that the total time needed of only 25 min to complete the 35 cycle PCR amplification. An optimized PCR with two-temperature approach for denaturing and annealing (Td and Ta) of DNA was also formulated with the PCR chip, with which the amplification of male-specific sex determining region Y (SRY) gene marker by utilizing raw saliva was successfully achieved and the genetic identification was in-situ detected right after PCR by the optical detection system.

Two strategies of stubborn biofouling strains surviving from NaClO membrane cleaning: EPS shielding and/or quorum sensing.

The declined performance of repeated chemically-enhanced-backwashing (CEB) seriously hampered the sustainable operation of membrane bioreactor (MBR) in long-term, and could be partially attributed to the strengthened anti-cleaning properties of residual stubborn microbes. Although plenty of research has been done towards either the model strains or the whole post-CEB microbial community, little was known about the resisting behavior of practical stubborn strains when confronting oxidative stresses induced by NaClO. Hence, this study isolated 21 strains from samples in a large-scale MBR plant with routine CEB treatment. To unravel how they survive and affect membrane fouling, their anti-oxidation ability, fouling potential and quorum sensing (QS) effect before and after NaClO stimuli were evaluated. The composition and molecular weight distribution of extracellular polymeric substance (EPS) were also investigated to understand their roles during the anti-CEB process. It was found that typical stubborn strains tended to secrete more EPS as protective shields, where polysaccharides (especially the ones >1 kDa) made major contribution. However, sometimes EPS could not well resist the stimuli, with consequent low survival rate and high intracellular ROS level. Under such circumstances, stubborn strains would rather choose to be sensitive with surged QS level and quick population regrowth to maintain vitality under the oxidative stresses. Both strategies aggravated biofouling and eventually enhanced the anti-cleaning properties of biofilm.

Electroconductive moving bed membrane bioreactor (EcMB-MBR) for single-step decentralized wastewater treatment: Performance, mechanisms, and cost.

Membrane bioreactor (MBR) is an advantageous technology for wastewater treatment. However, efficient nutrient removal and membrane fouling mitigation remain major challenges in its applications. In this study, an electroconductive moving bed membrane bioreactor (EcMB-MBR) was proposed for simultaneous removal of organics and nutrients from domestic wastewater. The EcMB-MBR was composed of a submerged MBR, filled with electrodes and free-floating conductive media. Conductive media were introduced to reduce energy consumption in an electrochemical MBR, to improve nitrogen removal, and to mitigate membrane fouling. The results showed that COD, total nitrogen, and total phosphorus removal was up to 97.1 ± 1.4%, 88.8 ± 4.2%, and 99.0 ± 0.9%, respectively, in comparison with those of 93.4 ± 1.5%, 65.2 ± 5.3%, and 20.4 ± 11.3% in a conventional submerged MBR. Meanwhile, a total membrane resistance reduction of 26.7% was obtained in the EcMB-MBR. The optimized operating condition was determined at an intermittent electricity exposure time of 10 min-ON/10 min-OFF, and a direct current density of 15 A/m2. The interactions between electric current and conductive media were explored to understand the working mechanism in this proposed system. The conductive media reduced 21% of the electrical resistivity in the mixed liquor at a selected packing density of 0.20 (v/v). The combination of electrochemical process and conductive media specially enhanced the reduction of nitrate-nitrogen (NO3--N) through hybrid bio-electrochemical denitrification processes. These mechanisms involved with electrochemically assisted autotrophic denitrification by autotrophic denitrifying bacteria. As a result, 5.2% of NO3--N remained in the effluent of EcMB-MBR in comparison with that of 29.5% in the MBR. Membrane fouling was minimized via both mechanical scouring and electrochemical decomposition/precipitation of organic/particulate foulants. Furthermore, a preliminary cost analysis indicated that an additional operating cost of 0.081 USD/m3, accounting for 10 - 30% increment of the operating cost of a conventional MBR, was needed to enhance the nitrogen and phosphorus removal correspondingly in the EcMB-MBR.

Electroporation of micro-droplet encapsulated HeLa cells in oil phase.

Electroporation (EP) is a method widely used to introduce foreign genes, drugs or dyes into cells by permeabilizing the plasma membrane with an external electric field. A variety of microfluidic EP devices have been reported so far. However, further integration of prior and posterior EP processes turns out to be very complicated, mainly due to the difficulty of developing an efficient method for precise manipulation of cells in microfluidics. In this study, by means of a T-junction structure within a delicate microfluidic device, we encapsulated HeLa cells in micro-droplet of poration medium in oil phase before EP, which has two advantages: (i) precise control of cell-encapsulating droplets in oil phase is much easier than the control of cell populations or individuals in aqueous buffers; (ii) this can minimize the electrochemical reactions on the electrodes. Finally, we successfully introduced fluorescent dyes into the micro-droplet encapsulated HeLa cells in oil phase. Our results reflected a novel way to realize the integrated biomicrofluidic system for EP.

[Triple arthrodesis with osteotomy for the treatment of stage IIB and stage III adult-acquired flatfoot deformity].

OBJECTIVE: To analyze the clinical outcomes of triple arthrodesis with osteotomy in the treatment of Stage IIB and Stage III adult-acquired flatfoot. METHODS: The authors reviewed 10 cases of adult-acquired flatfoot, including 3 cases of stage IIB adult-acquired flatfoot and 7 cases of stage III adult-acquired flatfoot. They were treated by triple arthrodesis with osteotomy of subtalar joint (STJ), talonavicular joint (TNJ) and calcaneocuboid joint (CCJ). The combined medial and lateral incisions were used to obtain adequate exposure for CCJ, STJ and TNJ. Then the cartilages of CCJ, STJ and TNJ were completely denuded and osteotomies to restore their proper alignments. The optimal positioning of hindfoot could be achieved and fixed by Kirschner wires. Two cannulated screws of 7.3 mm were delivered through the plantar aspect of heel to fix STJ. And then two 4.5 mm cannulated screws individually fixed TNJ and CCJ distal to proximal. Clinical evaluations were based on the AOFAS ankle-hindfoot scale and subjective assessments of pains, function, cosmesis and overall satisfaction. Radiographic evaluations included measurements of anterior-posterior talo-first metatarsal angle, lateral talocalcaneal angle, lateral talo-first metatarsal angle and an assessment of time to union for all arthrodeses. RESULTS: All patients were followed-up with a mean time of 13.2 (6 - 21) months. The average AOFAS ankle-hindfoot scale improved from 39.4 ± 4.4 preoperatively to 83.7 ± 2.6 postoperatively (P < 0.01). And the patients experienced subjective improvements in pain, function and cosmesis. Overall, all patients were satisfied. Radiographically, the rate of bone healing was 100%. The anterior-posterior talo-first metatarsal angle, lateral talocalcaneal angle and lateral talo-first metatarsal angle statistically improved. No complication, such as infection and un-union, was reported. CONCLUSION: Triple arthrodesis with osteotomy is an effective procedure for the treatment of stage IIB and III adult-acquired flatfoot deformity. It may relieve pains, correct structural deformities and obtain excellent clinical outcomes.

[Medial displacement calcaneal osteotomy with mini-incision for the treatment of acquired flexible flatfoot caused by posterior tibial tendon dysfunction].

OBJECTIVE: To investigate the clinical outcomes of medial displacement calcaneal osteotomy with mini-incision for the treatment of acquired flexible flatfoot caused by posterior tibial tendon dysfunction. METHODS: From 2005 to 2009, 10 patients (13 feet) of acquired flexible flatfoot with obvious heel valgus underwent medial displacement calcaneal osteotomy with mini-incision. The lateral skin incision of 3.0 - 4.5cm was made to explore the lateral calcaneal wall. Calcaneal osteotomy was performed from inferior and lateral to superior and medial, perpendicular to the longitudinal axis of calcaneal body. The distal segment was displaced medially for 1/3-1/2 width of calcaneal body and fixed by two parallel cannulated screws. All patients were evaluated at 6 weeks, 3 months, 6 months, 12 months and every 6 months pre- and post-operatively by clinical examinations and radiological studies. All patients were physically examined with an extended protocol of questionnaires and the AOFAS Ankle & Hindfoot Scales. The lateral view of full foot allowed an assessment of bone healing, calcaneus inclination angle (CI), talocalcaneal angle (TC) and talar first metatarsal angle (TMT). The AP view of full foot allows assessment of TC and TMT. The heel varus/valgus alignment could be evaluated on the axial radiographs of hindfoot. RESULTS: With a mean postoperative follow-up period of 20.3 months (range 7 - 55 Ms), all patients had bone union as confirmed by clinical examination and radiology. The AOFAS rating scale improved from a pre-operative mean of 50.3 to a mean of 80.2 at 6 months and a mean of 84.2 at last follow-up, without any complication of infection, nerve injure and so on. All radiographic parameters were statistically significant (P < 0.001), including CI, TC and TMT on the lateral view and TC and TMT on the AP view. The heel varus/valgus was corrected on the axial view. CONCLUSION: The medial displacement calcaneal osteotomy with mini-incision is a recommended procedure for the treatment of acquired flexible flatfoot with excellent clinical outcomes, correction of deformity and fewer complications.

Membrane autopsy deciphering keystone microorganisms stubborn against online NaOCl cleaning in a full-scale MBR.

The knowledge about membrane biofouling evolution in full-scale membrane bioreactor (MBR) applications is quite lacking, notwithstanding a few lab-scale investigations. For the first time, this study elaborated the effect of online NaOCl cleaning on the dynamic development of membrane biofilm microbiota during long-term operation of a large-scale MBR for municipal wastewater treatment (40,000 m3/d). Four times of membrane autopsies were conducted during 160 days operation to scrutinize the microbial community and concomitant organic foulants. The transmembrane pressure difference (TMP) development revealed limited effect of 30 min online NaOCl cleaning on long-term biofouling removal. NaOCl not only altered the structure of biofilm communities but also increased the richness and evenness on early fouling stages. Meanwhile, network analysis revealed the keystone taxa f_Comamonadaceae that played key roles in stabilizing community structure and developing anti-cleaning and irreversible fouling propensity of the biofilm. NaOCl cleaning also impacted the evolving of keystone taxa by intensifying the competition between the dominated taxa f_Moraxellaceae and other species during early fouling stages. Furthermore, the succession of the biofilm microbiota synchronously accelerated the TMP increase and the accumulation of organic foulants including polysaccharides, aromatic proteins and soluble microbial products during biofilm maturation. These identified key stubborn foulants shed light on limitations of current online NaOCl cleaning and provide guidance to optimize the efficiency of online chemical cleaning protocols in full-scale MBR operations.

Surface Grafting of Reverse Osmosis Membrane with Chlorhexidine Using Biopolymer Alginate Dialdehyde as a Facile Green Platform for In Situ Biofouling Control.

We report a new robust and green facile platform for nonoxidizing chemical grafting to simultaneously improve antifouling and antibacterial properties of thin film composite (TFC) polyamide (PA) reverse osmosis (RO) membranes. In this work, alginate dialdehyde (ADA) was used as a green platform to graft chlorhexidine (CH), a nonoxidizing chemical, on TFC-RO membrane surface. A synergistic effect due to ADA and CH grafting was revealed. The modified membrane surfaces were characterized using XPS, FT-IR, AFM, SEM-EDS, contact angle, and zeta potential analysis. A simple two-step Schiff base reaction was performed. Improved salt rejection performances were observed for the grafted PA membranes at the expense of negligible flux drop for the CH-ADA-PA membranes (38 to 42 L m-2 h-1) compared with the pristine PA membrane (45 L m-2 h-1). All the CH-ADA-PA membranes had excellent antibacterial activity against E. coli along with a highly superior resistance to the formation of biofilms. Organic fouling behaviors with a protein (bovine serum albumin, BSA) and a surfactant (dodecyl trimethylammonium bromide, DTAB) were investigated as typical foulants for the grafted PA membranes. The results indicated that the CH-ADA-PA membranes showed the best antifouling performance followed by the ADA-PA membranes, the pristine membrane being the most inferior. Hence, these results pave the way for a new robust and green bioinspired route for practical application in RO membrane fouling control.

[Study on P forms in extracellular polymeric substances in enhanced biological phosphorus removal sludge by 31P-NMR spectroscopy].

The present paper investigated phosphorus forms in the extracellular polymeric substances (EPS) using 31P-NMR spectroscopy, and analyzed the influential parameters for this method. The results showed that in the three investigated EPS samples five P forms were identified, including orthophosphate, orthophosphate monoesters, DNA, pyrophosphate and polyphosphate. And in the EPS extracted from A/A/O sludge and A/A/O-MBR sludge polyphosphate was the main phosphorus form. This indicated that P is contained in the EPS not only owing to the adsorption of orthophosphate, but also because EPS acting like the bacteria cells contributes to enhanced biological phosphorus removal. Furthermore the transformation of P forms in the EPS during the EPS extraction was found but limited within 1 h. It was found that with the NaOH solution added the polyphosphate in the EPS would partly convert to pyrophosphate but not go further to orthophosphate, while with pure water added P forms in the EPS were very stable. This means that after neutralization, the transformation of phosphorus forms could be avoided. Since the measurement of 31P-NMR spectroscopy was very sensitive to pH, which could affect the chemical shift of the peaks and cause peaks overlapping, the pH of EPS sample must be raised to 13.0 before the measurement.

Quantifying the dynamic evolution of organic, inorganic and biological synergistic fouling during nanofiltration using statistical approaches.

The dynamic process of membrane fouling was characterized during relatively long-term (30 d) continuous nanofiltration (NF) of a real wastewater secondary effluent, with the roles of organic, inorganic and biological foulants quantified via statistical analyses. The analyses were based on time-series data of physical properties (morphology, roughness, hydrophilicity and charge), chemical compositions (X-ray and infrared responses) and biomass (adenosine triphosphate, ATP) on the membrane surface during fouling evolution. The individual and interactive contributions of organic factor (typical functional groups), inorganic factor (Ca as a representative) and biological factor (ATP amount) to fouling were quantified via multiple linear regression coupled with variance partitioning analysis. About 78% of the variance of filtration resistance can be explained by these factors, among which 16% was contributed by individual effect of organics (via e.g. physical adsorption), 21% by organic-inorganic binary effect (in the form of e.g. Ca-complex), 13% by organic-biological binary effect (organics as the nutrient/product of microorganisms), and 24% by organic-inorganic-biological ternary interaction. Organic matter was universally involved in these effects. The interrelations among fouling factors, foulant layer properties and filtration time were comprehensively explored via redundancy analysis, which clearly delineated the fouling evolution into three major stages: Stage I (0-1 d) for initial fouling mainly due to rapid organic adsorption; Stage II (1-10 d) mainly for the gradual growth of Ca-organic combined fouling; and Stage III (10-30 d) for the eventual maturation of biofouling. These may provide foundations for a targeted fouling control based on foulant type or fouling stage.